The invention relates to a method and apparatus for filling of cellulose containing fiber material and liquid to steam phase in a preferably continuously working treatment vessel (a digester) at superatmospheric pressure for pulp production.
The main object of the invention is, in a simple way, to be able to feed into a treatment vessel and regulate the quantity of treatment liquid and fiber material so that the ratio between fiber material and liquid, (the wood/liquid ratio), will be as close as possible to the desired ratio for the process and cooking parameters which are desired.
Swedish Pat. No. 128,264 (see U.S. Pat. No. 2,680,683 also), which shows a feeding valve which mainly consists of a housing and a rotating rotor with pockets therein, which pockets are periodically filled and emptied, discloses conventional prior art apparatus. With such conventional apparatus it is possible with relatively good precision, to feed into a treatment vessel, a distinct quantity per unit of time of fiber material. With such conventional feed-in apparatus, the emptying of a rotor pocket takes place by turning the rotor so that the pocket communicates with an outer circulation pipe with ends connected to the digester and in which cooking liquor is being circulated. Thereby the fiber material is transported by the cooking liquor and is fed into the digester. When the pocket in such a device has emptied its content of fiber material, it is completely filled with cooking liquor of a volume which is greater than the volume of the cooking liquor which was present in the pocket just before it emptied its fiber material content. This means that the digester, when the feeder rotor is continuing to turn, has had a liquor volume corresponding to the volume of the fed-in fiber material tapped therefrom. In order to maintain the liquid balance of the digester, then, it is necessary by some accessory means to feed a quantity of liquid corresponding to the tapped-out quantity, into the digester as well as possible additional fresh treatment liquid. This often necessitates the utilization of high pressure pumps.
The present invention discloses a new method and an apparatus enabling to feed a digester with desired fiber material and necessary predetermined desired quantity of treatment liquid. Herewith due regard is taken not only to the necessary quantity fresh treatment liquid for the digesting process but also to the quantity of moisture in the fiber materials and also the quantity of condensate from the pretreatment as well as leakage from the high pressure side of the feeder to its low pressure side.